Method for producing silylated cellulose

Abstract

A method for preparing silylated cellulose is disclosed, which includes preparing a reaction product in the form of a paste and removing unreacted starting materials and / or by-products from the paste to form powdered silylated cellulose.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application is a U.S. national stage application under 35 U.S.C. 371 of International Application No. US23 / 080624, filed November 21, 2023, which is currently pending, and claims the benefit under 35 U.S.C. 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 63 / 432,713, filed December 15, 2022.

[0002] FIELD OF THE INVENTION A method for producing silylated cellulose is provided. More specifically, the method for producing silylated cellulose is available on a commercial production scale. [Background technology]

[0003] Introduction Current technologies for producing silylated cellulose are based on low volumetric yield slurry or solution processes. Some of these processes utilize high pressure, in which the cellulose is in a slurry of liquefied ammonia. Other processes utilize atmospheric pressure processes in large volumes of swelling solvent. These processes have the disadvantage of requiring very large volumes of swelling solvent and recrystallization solvent, generating large amounts of waste. Furthermore, the space-time yield of these processes is very low due to the volumetric requirements of the solvent. Therefore, these processes have not been commercially viable for large-scale use.

[0004] U.S. Patent No. 4,320,692 to Green discloses a method for preparing trimethylsilyl cellulose ethers, which involves reacting cellulose with hexamethyldisilazane in the presence of a small amount of catalyst. In a preferred method of carrying out this process, the reaction temperature is maintained between about 100°C and about 135°C. At temperatures below 100°C, the reaction is too slow to be practical, and at temperatures above 135°C, the reaction is found to be very unstable.

[0005] There is a need in the industry for a more volumetrically efficient process for preparing silylated cellulose, which process would also desirably operate at ambient pressure and / or utilize less solvent than existing processes. Summary of the Invention

[0006] Provided herein is a method for preparing silylated cellulose, the method comprising: 1) A) cellulose; B) a polar aprotic swelling agent; C) a catalyst; D) a silylating agent comprising a silylamine; and thereby forming a reaction mixture; 2) mixing the reaction mixture in a reactor equipped with a self-wiping mixing blade and heating the reaction mixture, thereby forming a reaction product comprising silylated cellulose. The starting materials used in this method include the starting materials A), B), C), and D) introduced above, and these starting materials are used in amounts sufficient to prepare the reaction product as a paste. DETAILED DESCRIPTION OF THE INVENTION

[0007] More specifically, the method for preparing the silylated cellulose introduced above comprises: 1) A) cellulose comprising repeating monomer units having more than 2.5 hydroxyl groups per monomer unit; B) a polar aprotic swelling agent; C) a catalyst; D) a silylating agent containing a silylamine having a silicon-nitrogen (Si—N) moiety; combining the starting materials, optionally including E) a solvent; thereby forming a reaction mixture; 2) mixing the reaction mixture in a reactor equipped with a self-wiping mixing blade and heating the reaction mixture at a temperature of 30°C to 150°C, thereby forming a reaction product comprising silylated cellulose. The starting materials, including A), B), C), and D), are used in amounts sufficient to prepare the reaction product as a paste.

[0008] The method may optionally further include one or more additional steps. For example, the method may further include A) drying the cellulose before step 1). Commercially available cellulose may contain adsorbed water. To minimize the formation of by-products, the cellulose may be dried to remove at least some of the water. Drying may be carried out by any convenient means, such as by exposing the cellulose to heat and / or reduced pressure or an inert gas stream.

[0009] The method may optionally further include, for example, adding E) a solvent different from B) the polar aprotic swelling agent in step 1) or step 2). Alternatively, the method may further include an additional step, prior to step 1), of dissolving C) a catalyst in one or both of B) the polar aprotic swelling agent and E) the solvent to form a catalyst solution. The resulting catalyst solution may be mixed with A) cellulose prior to step 1) (e.g., prior to adding D) the silylating agent to the reactor). For example, the catalyst solution may be mixed with A) cellulose for at least 10 minutes, or at least 15 minutes, while the catalyst solution may be mixed with A) cellulose for up to 1 hour before adding D) the silylating agent.

[0010] Alternatively, the method may further include an additional step comprising: D) forming a catalyst by a process comprising ex-situ reacting a portion of the silylating agent with an acid. Optionally, E) a solvent may be used to facilitate mixing of the silylating agent with the acid. When this step is added to the method, the silylating agent used to form the catalyst may be, but is not limited to, a silazane, such as those described below for starting material D). The silazane selected to form the catalyst may be the same as or different from the starting material D) used in step 1) to carry out the silylation reaction. This step may be carried out by any convenient means, such as by mixing, at room temperature and ambient pressure.

[0011] In step 2), the reaction mixture is mixed for 15 minutes to 24 hours or more, alternatively for 15 minutes to 24 hours, alternatively for 30 minutes to 2 hours. The temperature in step 2) may be 30°C to 150°C, alternatively for 50°C to 85°C, alternatively for 50°C to 80°C, alternatively for 55°C to 80°C. The pressure in step 2) may be 730 mmHg (97 kPa) to 790 mmHg (105 kPa), alternatively for 750 mmHg (100 kPa) to 770 mmHg (103 kPa). The reaction mixture and / or reaction product produced in step 2) has a paste consistency that cannot be mixed in a standard reaction vessel equipped with a single mixing blade, nor can the reaction mixture be easily pumped. When cooled to room temperature, the paste may form a solid. If a paste is formed in a reactor equipped with a single mixing blade, the paste solidifies on the mixing blade at room temperature and must be manually removed from the reactor (i.e., the intractable solids that form cannot be broken up in the reactor and cannot be pumped out of the reactor, as illustrated in Comparative Example 5 below). Therefore, a reactor capable of mixing a reaction mixture and reaction product having this consistency is used. This reactor has a self-wiping mixing blade and can be, for example, a kneader reactor or a sigma blade reactor. Without being bound by theory, it is believed that the self-wiping mixing blade can continuously break up fibrous, crystalline, and / or entangled components, maintaining mixing within the reactor and preventing the formation of intractable solids.

[0012] The method may further include step 3) of heating the reaction product at a temperature of >50°C to 105°C and a pressure of >0 kPa to <101 kPa, thereby forming a friable solid or powder comprising silylated cellulose. Alternatively, the temperature in step 3) may be 60°C to 105°C, or alternatively, 65°C to 90°C. Without being bound by theory, it is believed that step 3) removes most of the residual ammonia and residual D) silylating agent, thereby converting the reaction product into a friable solid that can be easily comminuted to form powdered silylated cellulose, which can be mixed and transported using gas or powder handling methods. The method may further include comminuted the friable solid by any convenient means, such as grinding, to form powdered silylated cellulose. Alternatively, comminuted may be performed during step 2) in a reactor equipped with self-wiping blades.

[0013] The method may optionally further include step 4) of washing the powdered silylated cellulose by combining the powdered silylated cellulose with F) a washing solvent, thereby removing any residual polar aprotic swelling agent, catalyst, and / or solvent, and / or any by-products that may be present. The washing solvent is not particularly limited; however, the washing solvent may be a low-boiling polar solvent that can dissolve residual starting materials and / or by-products without significantly solubilizing the silylated cellulose, and this can be used to facilitate evaporation from the silylated cellulose product. The washing in step 4) may be carried out by any convenient means, such as combining the washing solvent with the powdered silylated cellulose produced as described above in the reactor used in step 1) or in an agitated slurry vessel, and then draining the solvent after a sufficient period of time. The washing step may be repeated as many times as necessary, for example, 1 to 10 times.

[0014] The method may optionally further comprise step 5) removing the wash solvent by any convenient means such as filtration, heating, vacuum, and / or by purging with a gas, e.g., air or an inert gas such as nitrogen.

[0015] The resulting product is pure silylated cellulose produced with low waste and high volumetric efficiency. The silylated cellulose produced by this method has a DS of 2.0 to 3.0, alternatively 2.2 to 3.0, alternatively 2.4 to 3.0, alternatively 2.6 to 3.0, alternatively 2.8 to 3.0.

[0016] The starting materials used herein are described in more detail below.

[0017] A) Cellulose The starting material A), i.e., the cellulose used in the above method, has more than 2.5 to 3, or 3, hydroxyl groups per repeating monomer unit in the molecule. Cellulose is a polymer of β(1→4)-linked D-glucose repeating monomer units. Cellulose can have 200 or more repeating monomer units per molecule. Alternatively, cellulose can have at least 200, alternatively at least 300, alternatively at least 400, alternatively at least 500, alternatively at least 600, or alternatively at least 700 repeating monomer units, while cellulose can have up to 10,000, alternatively at most 9,000, alternatively at most 8,000, alternatively at most 7,000, alternatively at most 6,000, alternatively at most 5,000, or alternatively at most 4,000 repeating monomer units per molecule. Alternatively, cellulose can have 200 to 10,000, alternatively at most 400 to 8,000 repeating monomer units per molecule.

[0018] The type of cellulose may be, for example, microcrystalline cellulose or pulp cellulose. Sources of cellulose include, but are not limited to, cotton linters, pine, and tunisin (animal-derived cellulose). Cellulose is commercially available from a variety of sources.

[0019] B) Polar aprotic swelling agents The starting material B) used in the above method is a polar aprotic swelling agent. Examples of suitable polar aprotic swelling agents include N-methylpyrrolidone (NMP), N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), dimethyl sulfone, propylene carbonate, pyridazine, dimethylformamide (DMF), ethylene carbonate, sulfolane, tetrahydrothiophene-1-oxide, and hexamethylphosphoramide (HMPA).

[0020] The starting materials A) and B) are used in amounts such that the weight ratio of B) polar aprotic swelling agent to A) cellulose is <3:1, alternatively <1:1, alternatively <0.3:1 (B:A ratio). Alternatively, the B:A ratio may be at least 0.1:1, alternatively 0.11:1, alternatively 0.12:1, alternatively 0.13:1, alternatively 0.14:1, alternatively 0.15:1, while the B:A ratio may be at most <0.3:1, alternatively 0.29:1, alternatively 0.28:1, alternatively 0.27:1, alternatively 0.26:1.

[0021] C) catalyst The starting material C) in the above method is a catalyst capable of catalyzing the reaction between A) the hydroxyl groups of cellulose and D) the silicon-nitrogen (Si-N) portion of the silylating agent. Examples of suitable catalysts include ammonium salts such as ammonium chloride, ammonium trifluoroacetate, or ammonium triflate; saccharin; sulfonic acids such as methanesulfonic acid, p-toluenesulfonic acid, or trifluoromethanesulfonic acid (triflic acid); trifluoroacetic acid; trimethylsilyl chloride; or combinations thereof. Alternatively, the catalyst can be selected from the group consisting of ammonium chloride, ammonium trifluoroacetate, or saccharin. Alternatively, the catalyst can include (or be) ammonium trifluoroacetate.

[0022] The catalyst can be applied by several methods that will be understood by those skilled in the art. These can be C) adding the catalyst (such as ammonium trifluoroacetate) directly to the reactor, or C) dissolving the catalyst in B) a polar aprotic swelling agent or E) solvent, and then adding the resulting catalyst solution to the reactor. Alternatively, C) the catalyst can be formed by premixing certain silylating agents, such as silazanes or other silylamines (as described below for starting material D), with acids such as trifluoroacetic acid or triflic acid, and then charging the resulting mixture containing the catalytic silylammonium salt to the reactor.

[0023] The amount of catalyst will depend on various factors, including the type of catalyst and the temperature selected, but may be at least 0.01 wt.%, alternatively at least 0.1 wt.%, alternatively at least 0.3 wt.%, while the amount of catalyst may be up to 5 wt.%, alternatively up to 4 wt.%, alternatively up to 3 wt.%, alternatively up to 2 wt.%, alternatively between 0.1 wt.% and 5 wt.%, alternatively between 0.3 wt.% and 2 wt.%, based on the total weight of the starting materials A), B), C), and D) used in the process.

[0024] D) Silylation Agents with Si-N Moieties The starting material D) in the above method is a silylating agent comprising a silylamine having a silicon-nitrogen (Si—N) moiety. The Si—N moiety is reactive with the hydroxyl groups of A) cellulose. The silylating agent can be selected from a silazane, an aminosilane, or a combination thereof. For example, a silazane can be represented by the formula

[0025] [ka] wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R 7are each independently selected from the group consisting of H, an alkyl group of 1 to 18 carbon atoms, and an alkenyl group of 2 to 18 carbon atoms. Suitable alkyl groups include methyl, ethyl, propyl, and butyl, or methylethyl and propyl. Suitable alkenyl groups include vinyl, allyl, and hexenyl. Examples of suitable disilazanes include 1,1,1,3,3,3-hexamethyldisilazane (HMDZ), 1,3-ethyl-1,1,3,3-tetramethyldisilazane, 1,3-dipropyl-1,1,3,3-tetramethyldisilazane, 1,3-dibutyl-1,1,3,3-tetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-diallyl-1,1,3,3-tetramethyldisilazane, 1,3-dibutenyl-1,1,3,3-tetramethyldisilazane, and 1,3-hydrido-1,1,3,3-tetramethyldisilazane.

[0026] Alternatively, the silylating agent may be an aminosilane, which has the formula: R N x SiR 8 4-x wherein each R N is an amino functional group attached to silicon through a nitrogen atom, and each R 8 is R 1 As described above for R, each R is independently selected from the group consisting of H, an alkyl group of 1 to 18 carbon atoms, and an alkenyl group of 2 to 18 carbon atoms, and the subscript x is 1 to 3. N is the formula -NR 9 2, wherein each R 9 are independently selected from the group consisting of H, an alkyl group of 1 to 18 carbon atoms, or an aryl group of 6 to 18 carbon atoms.

[0027] The aminosilanes are exemplified by tris(dimethylamino)silane, bis(diisopropylamino)silane, (N,N-dimethylamino)trimethylsilane, trimethyl(amino)silane {HN—Si(CH)}, triethyl(amino)silane {HN—Si(CH—CH)}, tripropyl(amino)silane {HN—Si(CH)}, tributyl(amino)silane {HN—Si(CH)}, dimethylethyl(amino)silane, dimethylbutyl(amino)silane, trivinyl(amino)silane, dibutylethyl(amino)silane, tri(1-butenyl)(amino)silane, or triaryl(amino)silane. Suitable aminosilanes are known in the art and are commercially available, for example, from Sigma-Aldrich, Inc. (St. Louis, Missouri, USA) or Gelest Inc. (Morrisville, Pennsylvania, USA).

[0028] The starting material D) silylating agent is a silylating agent having a molar ratio of Si-N moieties of D) silylating agent to hydroxyl groups of A) cellulose of >0.67:1 to 4:1 (D Si :A OH D Si :A OH The ratio may be from 0.7:1 to 3.5:1, alternatively from 0.8:1 to 3.0:1, alternatively from 0.9:1 to 2.5:1, alternatively from 1:1 to 2.0:1, alternatively from 1.15:1 to 1.98:1, alternatively from 1.3:1 to 1.4:1.

[0029] E) Solvent The starting material E) used in the above method is any solvent different from B) the polar aprotic swelling agent. The solvent is not particularly limited and may be any solvent that can dissolve or disperse A) cellulose and / or C) catalyst together with one or more other starting materials. For example, the solvent may include an aliphatic hydrocarbon such as hexane, an aromatic hydrocarbon such as toluene or xylene, a halogenated hydrocarbon such as carbon tetrachloride, or an ether such as tetrahydrofuran.

[0030] The amount of solvent depends on various factors, including the type and amount of catalyst selected. However, the amount of solvent can be ≧0 based on the combined weight of A), B), C), and D). Alternatively, the amount of E) solvent can be 0, or >0, while the amount of solvent can be up to 15 times the weight of the catalyst, or up to 12 times the weight of the catalyst. Without being bound by theory, it is believed that it is desirable to eliminate or minimize the amount of solvent for volumetric efficiency.

[0031] F) Washing solvent Starting material F) in the above method is any washing solvent that can be used to remove residual starting materials and / or by-products from the silylated cellulose produced by this method. Starting material F) may be different from the above starting materials B) and E). Examples of suitable washing solvents include water, ketones such as acetone, monohydric alcohols such as methanol or ethanol, or acetone. Without being bound by theory, it is believed that ketones such as acetone can effectively remove both polar and non-polar residues, while being easily removed from the silylated cellulose under reduced pressure.

[0032] How to use The silylated cellulose prepared as described herein can be used in a variety of end uses. For example, the silylated cellulose can be used in place of the cellulose derivatives described in U.S. Pat. No. 10,851,180 in optical films for image display devices. Alternatively, the silylated cellulose prepared as described above can be used as a thickening polymer in personal care applications (such as cosmetic or sun care formulations) in addition to or instead of the silylated cellulose polymers disclosed in WO 2022 / 066591. [Example]

[0033] These examples are provided to illustrate the invention to one of ordinary skill in the art and should not be construed as limiting the scope of the invention as set forth in the claims. The starting materials used in the examples are summarized in Table 1 below.

[0034] [Table 1]

[0035] Stripping reactions In this Example 1, cellulose was silylated in a Sigma Blade-type mixer (reactor) by charging 243 grams of microcrystalline cellulose, followed by a pre-dissolved solution of 68.25 grams of DMSO and 6.07 grams of NH4Cl, and mixing for 10 minutes. 483.25 grams of HMDZ was charged to the reactor, and the hot oil supply for heating the reactor was set to 90°C. When the temperature of the reaction mixture stabilized, the reactor was held at that temperature for 1 hour. Upon completion of the reaction, the resulting reaction product was a paste with a thick, taffy-like appearance. After holding the temperature, a vacuum was pulled to <200 Torr and held for 1 hour to prevent liquid from dripping into the vacuum flask. While the vacuum was held, the reaction product changed from a paste to a flaky, crumbly powder. 547.2 grams of the resulting crude product was recovered. The resulting silylated cellulose had a DS of 3.0.

[0036] In this Example 2, cellulose was silylated in a Sigma Blade-type mixer (reactor) by charging 304 grams of pulped cellulose, followed by a pre-dissolved solution of 86.4 grams of DMSO and 6.07 grams of NH4Cl, and mixing for 25 minutes. 604.1 grams of HMDZ was charged to the reactor, and the hot oil supply to the reactor was set to 90°C. When the temperature of the reaction mixture stabilized, the reactor was held at that temperature for 1 hour. Upon completion of the reaction, the material was a paste with a thick, taffy-like appearance. After holding the temperature, a vacuum was pulled to <200 Torr and held for 1 hour to prevent liquid from dripping into the vacuum flask. While the vacuum was held, the reaction product changed from a paste to a flaky, crumbly powder. 678.35 grams of crude product was recovered. The resulting silylated cellulose had a DS of 2.4.

[0037] Reaction with stripping, followed by washing and filtration through a pressure filter In this Example 3, cellulose was silylated in a Sigma Blade mixer by charging 242 grams of pulped cellulose, followed by a pre-dissolved solution of 68.4 grams of DMSO and 6.0 grams of NH4Cl, and mixing for 10 minutes. 484 grams of HMDZ was charged to the reactor, which was then heated to 73°C and held for 1 hour. Upon completion of the reaction, the reaction product was a paste with a thick, taffy-like appearance. After holding at approximately 73°C, a vacuum was pulled to <200 mmHg and held for 1 hour after the dripping stopped. While the vacuum was held, the reaction product changed from a paste to a flaky, crumbly powder. 540.9 grams of the resulting crude product was recovered.

[0038] The crude product was loaded into a pressure filter and acetone was added until the level was just above the solids. The resulting material was mixed by hand, held for approximately 15 minutes, and then drained. Additional acetone was added to the filter until the level was just above the solids, mixed by hand, held for approximately 15 minutes, and then drained. The final acetone wash was added to the filter until the level was just above the solids, mixed by hand, held for approximately 15 minutes, and then drained. The pressure filter was then sealed, a light N2 purge was applied over the filter, and the filter was allowed to stand overnight. In the morning, the resulting silylated cellulose was removed. The silylated cellulose contained a total silicon DS of 3.0.

[0039] Reaction with stripping, followed by washing and filtration through a Buchner funnel In this Example 4, cellulose was silylated in a Sigma Blade mixer by charging 234.7 grams of pulped cellulose, followed by a pre-dissolved solution of 68.2 grams of DMSO and 6.0 grams of NH4Cl, and mixing for 10 minutes. 484 grams of HMDZ was charged to the reactor, and the reaction mixture was then heated to 73°C and held for 1 hour. Upon completion of the reaction, the resulting reaction product was a paste with a thick, taffy-like appearance. After holding at approximately 73°C, a vacuum was pulled to <200 mmHg and held for 1 hour after the dripping stopped. While the vacuum was held, the reaction product changed from a paste to a flaky, crumbly powder. 571.52 grams of the resulting crude product was recovered.

[0040] 22.77 grams of the crude product was loaded into a Buchner funnel in a hood. 79 grams of acetone was added to the funnel along with the crude product and mixed by hand for 1 minute. The acetone was then drained by applying a vacuum to the drain flask while the crude product and acetone were mixed by hand. Another 109 grams of acetone was added and mixed / drained in the same manner. Another 100 grams of acetone was then added, mixed, and drained in the same manner. The remaining sample was spread thinly on a plate in a hood overnight to allow the remaining acetone to evaporate. In the morning, 19.37 grams of dry powdered silylated cellulose was recovered. The silylated cellulose contained a total silicon DS of 3.0.

[0041] Comparative Example - Non-Self-Wiping Blade (Single Agitator Shaft) In this Example 5, cellulose was silylated in a horizontal plow-type mixer by charging 2.64 kg of pulped cellulose, followed by a pre-dissolved solution of 740 g of DMSO and 65.4 g of NH4Cl, and mixing for 30 minutes. The mixer was heated to 90°C. When the internal temperature reached 68°C, 5.25 kg of HMDZ was charged over 10 minutes. The reactor was held at 90°C for 1.5 hours; however, high amperage was observed. When a vacuum was pulled on the system, the agitator failed and could not be restarted. Upon opening the mixer, it was observed that the entire volume of the mixer was filled with a hardened foam that had to be manually trimmed from the mixer.

[0042] Industrial Applicability Without being bound by theory, it is believed that the methods described herein can provide silylated cellulose with a DS > 2, or DS > 2.3, or DS ≥ 2.4-3.0. Examples 1-4 demonstrated that silylated cellulose with a degree of substitution ≥ 2.8 can be prepared by the method of the present invention in a reactor equipped with a self-wiping blade. Examples 1-4 and 5 demonstrated that the method of the present invention, employing a post-reaction stripping step, offers the advantage of providing silylated cellulose in the form of an easily transportable powder in a volumetrically efficient process that does not require the use of solvents during the silylation reaction. Furthermore, the method of the present invention is suitable for commercial-scale production of silylated celluloses, such as silylated cellulose. The above examples demonstrated that the method can produce batches of silylated cellulose of 500 g or more, or 600 g or more, or 1 kg or more, or 3 kg or more.

[0043] Without being bound by theory, it is believed that the method of the present invention may provide the additional benefit of minimizing or eliminating yellowing of the silylated cellulose produced in step 2) by conducting the silylation reaction at a temperature of 85°C or less.

[0044] Definitions and Use of Terms All amounts, ratios, and percentages herein are by weight unless otherwise specified. The articles "a," "an," and "the" each refer to one or more unless otherwise specified. The singular includes the plural unless otherwise specified. The "Summary" and "Abstract" are incorporated herein by reference. The transitional phrases "comprising," "consisting essentially of," and "consisting of" are used as set forth in Sections §2111.03 I, II, and III of the Manual of Patent Examining Procedure, Ninth Edition, Revision 08.2017, Last Revised January 2018.

[0045] DS, or degree of substitution, is defined as the average number of hydroxyl groups per monomer unit of the silylated cellulose. DS is determined by ATR-FTIR as follows: The degree of substitution (DS) of -SiR3 in the silylated cellulose prepared by the method described herein was determined using a technique known in the art based on attenuated total reflectance-Fourier transform infrared spectroscopy, which analyzes the spectral peak areas calculated in MATLAB using the spectral parameters provided in Table 2 along with the DS values ​​determined as reported in Table 3.

[0046] [Table 2]

[0047] [Table 3]

[0048] Abbreviations used herein have the definitions in Table 4.

[0049] Table 4

Claims

1. 1. A method for preparing silylated cellulose, comprising: １） A) a cellulose comprising repeating monomer units having >2.5 to 3 hydroxyl groups per monomer unit; B) a polar aprotic swelling agent; C) a catalyst; D) a silylating agent comprising a silylamine having a silicon-nitrogen moiety; thereby forming a reaction mixture; 2) mixing the reaction mixture in a reactor equipped with a self-wiping mixing blade and heating the reaction mixture at a temperature of 30°C to 150°C, thereby forming a reaction product comprising the silylated cellulose having a degree of substitution >2, wherein the starting materials are used in amounts such that the reaction mixture or the reaction product is a paste.

2. 10. The method of claim 1, further comprising A) drying the cellulose prior to step 1).

3. 3. The method of claim 1 or claim 2, further comprising, prior to step 1), C) dissolving the catalyst in B) the polar aprotic swelling agent, E) a solvent, or a combination thereof.

4. 4. The method of claim 1, wherein B) the polar aprotic swelling agent and A) the cellulose are used in amounts such that the weight ratio of B) the polar aprotic swelling agent:A) the cellulose is 0.1:1 to <3:1 (B:A ratio).

5. D) the silylating agent and A) the cellulose have a molar ratio of silicon-nitrogen moieties to hydroxyl groups of >0.5:1 to 4:1 (D Ｓｉ : A ＯＨ The method according to any one of claims 1 to 4, wherein the amount of the hydroxybenzoate is such that the ratio of the hydroxybenzoate to the hydroxybenzoate is 0.01 to 0.

01.

6. The method of any one of claims 1 to 5, wherein the catalyst comprises ammonium chloride or ammonium trifluoroacetate.

7. The method of any one of claims 1 to 6, wherein the method further comprises C) forming the catalyst by a process comprising ex-situ reacting a silazane with an acid.

8. 8. The method of any one of claims 1 to 7, wherein step 2) is carried out at a pressure of from 730 mmHg (97 kPa) to 790 mmHg (105 kPa).

9. The method according to any one of claims 1 to 8, wherein step 2) is carried out at a temperature of from 50°C to 85°C.

10. 10. The method of claim 1, wherein the method further comprises step 3) heating the reaction product at a temperature of >50° C. to 90° C. and a pressure of >0 kPa to <101 kPa and pulverizing the reaction product, thereby forming a powdered silylated cellulose.

11. 11. The method of claim 10, further comprising step 4) washing the powdered silylated cellulose 1 to 10 times by combining the powdered silylated cellulose with F) a washing solvent.

12. 12. The method of claim 11, wherein E) the washing solvent is removed by heating, by vacuum, and / or by purging with a gas.

13. The process according to any one of claims 1 to 12, wherein the reactor is a kneader reactor or a sigma blade mixer.

14. 13. The method of any one of claims 1 to 12, wherein the silylated cellulose is produced in an amount of at least 500 grams.

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